1. Field
One embodiment of the present invention relates to an IP broadcast system for broadcasting a TS (transport stream) of a plurality of programs through an IP broadcast network from a broadcast station to a broadcast receiver, and a multiplexer, a receiving apparatus and method used in the IP broadcast system.
2. Description of the Related Art
In recent years, the use of an IP broadcast system has extended for transmission of the broadcast contents to the users of the broadcast receivers through an IP network in addition to the transmission of the broadcast contents on a broadcast wave to the broadcast receivers from a broadcast station. Also, in the IP network, a large-capacity quality-controlled wide-area broadcast network called contents distribution network (CDN) or next-generation network (NGN) has come to be used widely. In these networks, the coded data of high-definition images are transmitted, and applications include video on demand (VOD) and IP broadcast programs.
Normally, a user datagram protocol (UDP) stream independent for each program is transmitted without multiplexing. In this case or especially in the case where a plurality of simultaneous programs are received by a set-top box (reproducing apparatus) for the IP broadcast, the requirement must be met for the process of simultaneous reception of a plurality of UDP streams, and the set-top box is correspondingly complicated, leading to an increased cost.
Although a method of multiplexing a plurality of programs using a transport stream (TS) according to Moving Picture Experts Group 2 (MPEG2) is available, the simultaneous processing of programs is complicated and a delay is caused.
In the normal network, the packet length is limited. In CDN or NGN, on the other hand, packets of some length have come to be transmitted as they are. A long packet can improve the throughput (transmission efficiency). The conventional packet length of about 1500 bytes, however, cannot exhibit the network performance sufficiently.
In the prior art, a communication terminal device (Jpn. Pat. Appln. KOKOAI Publication No. 2006-60631) and a network relay device (Jpn. Pat. Appln. KOKOAI Publication No. 2002-9832) are available for reducing the network load by multiplexing and transmitting a plurality of packets in one frame.
In the communication terminal device and the network relay device described above, a plurality of packets are multiplexed in one frame for communication but the TSs of a plurality of programs are not multiplexed as in the IP broadcast system described above.